Functional relationship and regulation of G-protein coupled receptors in salivary acinar cell plasma membrane) In addition to classical neurotransmitters acetylcholine and noradrenaline, increasing numbers of neuropeptides including substance P, calcitonin, VIP, serotonin, etc, were identified to be involved in the regulation of saliva secretion by interacting with their specific plasma membrane receptors. However, little is known about the functional relationship between these receptors in perspective of saliva secretion regulation. To approach this system with less complexity and more confidence, in vitro cultured salivary acinar cells are being used to conduct experiments to characterize plasma membrane (PM) receptors which are involved in stimulated secretion. Specific ligand or analog binding assay will be conducted to identify and classify the PM receptors, for the receptors with low copies on the PM, Ca++ response or RT-PCR will be utilized to fulfill the aim. Monitoring the change of marker (eg. amylase) and total protein concentration in the media after incubation of cells with different combination of receptor specific agonist/antagonist will be used to reveal the possible functional relationship of different PM receptors in perspective of salivary protein secretion. Further experiments will be designed to investigate the mechanisms involved in regulation between different receptors function such as desensitization/resensitization of receptor, signal transduction, and gene expression. Key words: salivary acinar cells, G-protein coupled receptor, saliva secretion,